1. Field of the Invention
The present invention relates to an image pickup apparatus and, more particularly, to an image pickup apparatus having a touch sensor for detecting touch coordinates.
2. Description of the Related Art
Hitherto, a release switch of a push-button type is generally provided for an image pickup apparatus called a camera, and the release switch has a non-depression state (which is generally a non-manipulated state in which the switch is not depressed), a full depression state in which a push-button causes the release switch to be depressed up to a maximum depression at which point the release switch is fully switched, and a half depression state as an intermediate state between them. In the half depression state (hereinbelow, referred to as SW1) of the release switch, photographing preparation operations such as autofocus control, autoexposure control, and auto white balance control are instructed. Further, when the release switch is set into the full depression state (hereinbelow, referred to as SW2), the actual photographing operation instruction (photographing instruction) is performed.
In a recent digital camera in which an object image is displayed on a liquid crystal panel screen so that a user can photograph the object image while confirming it on the screen, there is a case where a touch panel is used as an operation instruction unit. Among such cameras, there is a camera which is designed to use the touch panel to provide an operation instruction so that the camera operates as if a mechanical release switch is operated in a two-step manner of the half depression SW1 state and the full depression SW2 state.
As such a kind of camera, there is a camera in which a touch panel which can detect a pressure of finger pressing is used. This camera is arranged such that if it is detected that the panel is depressed and the pressure of the finger pressing is equal to or less than a certain threshold value, the photographing preparation operation is instructed, while if the pressure exceeds the threshold value, the photographing operation is instructed (refer to Japanese Patent Application Laid-Open No. 2007-236008).
There is also a camera in which a touch panel which can detect an area of finger pressing is used. This camera is arranged such that if the area of finger pressing is detected by using such a touch panel and the area is equal to or less than a certain threshold value, the photographing preparation operation is instructed, while if the pressure exceeds the threshold value, the photographing operation is instructed (refer to Japanese Patent Application Laid-Open No. 2007-093967).
There is also another camera which is designed to use two touch sensors such that the camera operates as if the mechanical release switch is operated in a two-step manner of the half depression SW1 state and the full depression SW2 state, thereby suppressing a camera shaking. In such a camera construction, the photographing preparation operation is instructed when the two sensors are touched, while upon detaching the finger from one of the two sensors, the photographing operation is instructed (refer to Japanese Patent Application Laid-Open No. H11-160776).
Although the methods of attaining the states SW1 and SW2 of the release switch using the touch detection unit have existed hitherto as mentioned above, a problem still remains in any of the above related arts and a countermeasure for solving such a problem is demanded.
For instance, in the example using the touch panel which is arranged to detect the pressure or the touch area of the finger pressing, it is necessary to strongly press the liquid crystal screen to attain the full depression SW2 state of the release switch, so that there is such a problem that a possibility of occurrence of the camera shaking rises.
In addition, since the touch panel which is arranged to detect the pressure or the touch area of the finger pressing is necessary, it is difficult to realize an image pickup apparatus by using a general low-cost touch panel which outputs only touch coordinates. The touch panel is thus difficult and costly to manufacture.
Further, since the example using the two touch sensors requires the two sensor devices, this may be a factor of causing an increase in costs and also results in such a problem that an operation procedure is complicated and is hard to be learned, and it is also difficult to operate with one hand.